Disposable absorbent articles are currently used in many different applications, including diapers and training pants for infants and children, feminine care products such as sanitary napkins or tampons, adult incontinence products, and health care products such as surgical drapes or wound dressings. The disposable absorbent article usually comprises a topsheet, a backsheet and an absorbent core positioned between the backsheet and the topsheet. Depending on the type of use involved, disposable absorbent articles can be subjected to one or more insults from aqueous liquids such as water, urine, menses or blood. As a result, the backsheet materials of these disposable products are typically made of liquid impermeable materials, such as polypropylene or polyethylene films, which exhibit sufficient strength and handling capability so that the disposable absorbent article retains its integrity during use by the wearer and does not allow leakage of the liquid from the product.
Many disposable absorbent articles can be difficult to dispose of into an aqueous environment. For example, attempts to flush many disposable absorbent articles down the toilet can cause blockage of the toilet or pipes connecting the toilet to the sewage system. In particular, the backsheet materials used in these disposable absorbent articles generally do not dissolve, disintegrate or disperse readily when flushed down a toilet so that the disposable absorbent article cannot be disposed of in this manner. If the backsheet materials are made very thin to reduce the overall bulk of the disposable absorbent article and reduce the likelihood of blockage of the toilet or sewage pipe, it may not exhibit sufficient strength to prevent tearing or ripping as the material is subjected to the stresses of normal use by the wearer. In a number of instances, it would be desirable to be able to flush these disposable absorbent articles down the toilet. These include certain catamenial products, known as labial or interlabial sanitary napkins or pads. Interlabial pads have the potential to provide greater freedom from inconvenience because of their small size and reduced risk of leakage. Indeed, these interlabial pads are small enough to be easily flushed down the toilet, typically without clogging it or the sewage pipes. Even though flushable, such products could put a significant environmental demand on sewage treatment or septic tank systems if they are not readily susceptible to degradation and disintegration after being flushed.
Various attempts have therefore been made to solve this problem. For example, U.S. Pat. No. 6,514,602 to Zhao, et al. describes a water-flushable film that contains a water-impervious biodegradable layer and a water-dispersible layer. The biodegradable layer includes from 65% to 100% of a water-insoluble biodegradable thermoplastic polymer and from 0% to 30% of a water-soluble thermoplastic polymer, and the water-dispersible layer contains from 60% to 100% of a water-soluble thermoplastic polymer and from 0 to 40% of a water-insoluble thermoplastic polymer. In one example, the film contains a 1st layer of 25% Bionolle (polybutylene succinate adiapte copolymer) and 75% PEO; a 2nd layer of 25% Bionolle and 75% PEO; and a 3rd layer of 100% Bionolle. Despite imparting some barrier properties to the film, various problems nevertheless remain with such films. For instance, several of the synthetic biodegradable polymers employed in Zhao, et al. can lead to an undesirable stickiness when dry or wet, as well as relatively poor mechanical properties. The polymers are also expensive. Furthermore, while the synthetic biodegradable polymers employed therein can be melt processed, they are not generally renewable, which limits the overall renewability of the film. Unfortunately, polymers that are both biodegradable and renewable are often difficult to melt process into a film.
As such, a need currently exists for a flushable and biodegradable film that has good mechanical properties, and yet is able to employ at least some renewable components.